$c(n) = -7 + 6(n - 1)$ Find the $4^\text{th}$ term in the sequence.
This is an explicit formula. All we have to do is plug $n=4$ in the formula to find the $4^\text{th}$ term. $\begin{aligned} c({4}) &= -7 + 6 ({4} - 1) \\\\ &= 11 \end{aligned}$ The $4^\text{th}$ term is $11$.